Printed circuit boards are an increasingly common component in all types of electronic devices. It is customary practice in the circuit board industry to conduct an integrity test on each newly manufactured printed circuit board to check for broken or disconnected circuits. Integrity testing entails making electrical contact between a number of predetermined locations on the printed circuitry and specially adapted electrical diagnostic equipment. The equipment measures an integrity parameter at predetermined locations on the printed circuit board and compares the measurements with standard values.
Besides integrity testing, printed circuit boards are frequently subjected to functionality testing. Functionality testing entails placing test probes into contact with the input and output of the printed circuit board, and into contact with specific predetermined locations along the printed circuit board.
Therefore, both integrity and functionality testing, as well as other types of analyses, require contact between test probes and the printed circuit board. This contact must be precise, and must be made in a manner which will not damage the printed circuit boards.
In U.S. Pat. No. 5,311,120, I described a particular test fixture suitable for testing printed circuit boards, both for integrity and functionality. Although the test fixture disclosed in U.S. Pat. No. 5,311,120 has been found to be a major improvement over prior art devices, problems still remain. One such problem is that the driving mechanism for moving the printed circuit board into contact with the test probes is provided by a number of hydraulic pistons which apply pressure at a relatively small number of points on the plate holding the printed circuit board. Such driving mechanism is not as solid and precise as desirable.
Another problem is that the physical size of test fixtures such as disclosed in U.S. Pat. No. 5,311,120--which opens upwardly (like a suitcase)--take up an excessive amount of physical space within a user's test facility.
Accordingly, there is a need for a test fixture capable of inexpensively and efficiently testing printed circuit boards which is at once compact, rigid and precise in operation.